When attempting to embed Qlik Sense in an iFrame (via the single configurator), the iFrame does not render (appears blank) when attempting to access the page from a machine outside the Qlik server.
The page is accessible only from within their server, or via an incognito/private tab (Chrome/Firefox) outside the server.
Environment
Qlik Sense Enterprise on Windows
The user accessing the page needs to ensure they are not blocking Qlik from setting browser cookies. The user can try temporarily disabling the option to block ALL 3rd party cookies in Chrome, for example, and observe if the iFrame now renders.
NOTE: While the page may be accessible outside the server via a private window, not all browsers treat "private" windows the same; some allow cookies and others don't.
The same problem may occur also in case the "SameSite" attribute is not set to "None" in the virtual proxy.
Follow this article and set the "SameSite" attribute to "None": Missing SameSite attribute blocks requests in Chrome 80 and later - Too many sessions in parallel
More information about Sense Site attribute can be found here: SameSite cookie attribute